


Against Company Policy

by MeGaLoTrash



Category: Undertale (Video Game)
Genre: Dry Humping, Ecto-Penis (Undertale), Frottage, Heavy flirting, M/M, Not Related Sans/Gaster, Power Play, Rough Sex, Semi-Public Sex, Sexual Tension, Switching, Workplace Sex
Language: English
Status: Completed
Published: 2018-06-09
Updated: 2018-06-09
Packaged: 2019-05-20 04:32:40
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,709
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14887712
Author URL: https://archiveofourown.org/users/MeGaLoTrash/pseuds/MeGaLoTrash
Summary: Working overnight at the labs has it's perks. Quiet working conditions, more time off, an assistant who won't stop flirting with you...Sanster for anon, hope you enjoy!!





	Against Company Policy

Gaster wasn’t a monster who spooked easily, but there was no way to hide the way he jumped while the kettle in the break room whistled loudly. In his defence, he had been letting his mind wander and the screech cut like a knife through the silence of the lab’s abandoned halls. With a shaking hand he poured water over his third cup of instant coffee that night, fully expecting to be back for more within the hour. He didn’t mind working through the night, in fact he found the solitude it granted leant itself to productivity. The reason he was so on edge wasn’t due to dimly lit halls or the oppressively low ceilings, but rather because tonight he wasn’t fully alone. 

Picking up his now filled cup, Gaster peeked around the break room door before swiftly walking back to his desk. He knew he was boarding on paranoid behaviour, but he couldn’t risk running into Sans unprepared. His colleague already had a habit of sneaking up on him and now they were alone Gaster fully expected Sans to try and surprise him at some point tonight. Considering just how close Gaster was to jumping the other skeleton’s bones, being caught off guard was a risk he couldn’t afford to take. 

Sans had been working in Hotland’s labs for a few years now, being moved onto the same team as Gaster a few months prior to tonight. Being one of the very few skeleton monsters in the underground gave them a common ground for conversation, easily building up a rapport despite Sans’s awful sense of humour. The close quarters they worked in allowed for more bonding opportunities and naturally developed into a kind of competitive flirting. Gaster had found the exchange stimulating at first compared to the monotony of lab work. He actively played along with trying to one-up whatever Sans threw at him. When the lab assistant started showing up in his dreams, tangled in his bedsheets with little else on, Gaster realised that their playful banter had gone too far.

The problem with working together on such an intense project meant that Gaster couldn’t just avoid Sans until his infatuation went away. While he wasn’t Sans’s boss, he was a more senior member of staff and did hold a certain amount of power over him. That both repulsed him and excited him in equal measures. Gaster didn’t like the idea of taking advantage of a subordinate. But with the way Sans was relentlessly flirting with him since moving teams, it was hard to think of him as anything but willing. Between that and his own suppressed desires Gaster was hopeless. Visions of Sans in his bed bled over into his conscious mind, with the bed being replaced with whatever Sans happened to be nearest too. 

Which was why his soul had sunk when he had seen Sans’s name assigned to his for the shifts this week. If being with Sans all day was hard enough, he could only imagine what it was going to be like when they were shut in overnight without the restrictions of social performativity. Even the simple exchange they had shared when clocking in had been laced with suggestive undertones. Gaster likened his experience tonight to being in a pressure cooker seconds away from boiling over. He just needed to make it through the night before going home and giving into primitive urges in the privacy of his bedroom. Gaster tried to focus back on his work, safe in the knowledge that he would have no issues with being able to complete it within the allotted time. Alone. 

That sentiment lasted less than an hour.

It became clear quite quickly that there was no way Gaster was going to be able to run these numbers on his own if he wanted accurate results. He then proceeded to try and prove himself wrong and stall in any way possible, but all that did was increase his frustration levels. The truth of the matter was that this wasn’t a solo task, and of course, Sans just happened to be extremely gifted with numbers. Swallowing his pride, along with any other sensations he had from thinking about the other skeleton, Gaster punched Sans’s number into his pager. He took a deep breath and tried to mentally prepare himself for what was to come, repeating the mantra of how inappropriate it was to lust after a someone at the workplace. 

“hey- what’s up doc?” 

Gaster had to grip hold of the paper he was working on to stop himself from jumping again, a detail that Sans would surely pick up on. Sans was leaning against the doorway with a completely unphased expression like he hadn’t just materialized out of nowhere. It was clear from a glance that Sans was taking liberties with only Gaster there to keep him in check. He was wearing a scruffy lab coat that was far too large for his frame, most likely for comfort, and his square-rimmed glasses were sitting crooked across his face. His tie wasn’t done correctly either. It was just haphazardly thrown around his cervical vertebrae just waiting for Gaster to pull it tightly and-

“I really wish you’d spend as much time on your research as you did watching those old human cartoons,” Gaster muttered, miming going back to look over his papers and shutting down the sinful thoughts that were plaguing him before they could take root. 

“you’re giving yourself away ‘dings-” Sans countered, waiting until he had Gaster’s full attention before adding “-must have watched ‘em yourself if you know where it’s from.”

 _Shit_. Gaster had walked right into that one and his assistant was going to milk it for all it was worth. Sans waited a few moments, enough time for Gaster to try and think of a rebuttal before he yawned dramatically. The sight of Sans’s untucked shirt rising up and exposing part of his spine made Gaster choke on his words. He tried to disguise it as a conveniently timed cough but he knew that Sans was already hyper-focused on everything he did. However, the other skeleton didn’t poke fun or rub in his victory. Sans continued to stretch while pretending he wasn’t looking in Gaster’s direction. It was almost like Sans wasn’t just doing this just to push Gasters buttons. Like he wanted Gaster to see more than he should...

But that line of thought was dangerous. Not to mention it was making the front of Gaster’s work pants feel tight around his magic. 

“I need help running these numbers.” Gaster said while gathering up the papers he wanted Sans to look over, thankful that his desk was currently providing convenient cover for his lower half. 

“aww, and here i was thinking you just wanted to see me.” 

Sans gave Gaster a wink before pushing himself off the door frame and heading towards his desk. Instead of taking the papers and sitting on any of the spare chairs in the room, Sans decided to lean over Gaster’s shoulder instead. Sans was doing a very good job of acting like he was completely focused in on their work even though every brush of his arm against Gaster’s was making the tension between them even more tangible. Gaster managed to put up with the close working quarters for a good five minutes before he started to break.

“Do you have to stand...there?”

Gaster knew that he was falling for the bait that Sans was dangling in front of him. It wasn’t that he had forgotten where they were, or forgotten that Sans was his assistant, but he was losing the ability to care. Sans was intent on tempting fate and Gaster was like a moth to a flame. 

“just trying to make it a little more fun.” Sans teased, the chuckle that followed causing a hot air to tickle the base of Gaster’s skull. “maybe you’re work ethic will rub off on me, i’ve been finding it awful hard to focus.” he leaned in a little further, taking in an exaggerated breath in before dropping his voice low enough to make Gaster shiver. “too many distractions.”

_Fuck this._

“That’s unacceptable.” Gaster spun his chair around towards Sans in an unexpected moment of spontaneity, catching the other skeleton off guard and making him fall into him. Sans’s spluttering reaction was just what Gaster had been hoping for. He moved his hands over where Sans was bracing himself, limiting his tormentor's ability to pull back. “As your superior, I should be looking for ways to punish you.”

“shit. gaster.” 

Gaster had to bite back a groan when he heard his name being said like that. He ignored any hesitations or moral standing, deciding to test just how far he could push this. Gaster pulled Sans closer, Sans _whimpered_.While Gaster was a fan of Sans’s usual cocky expression, he couldn’t deny that that heavy blush forming under the rim of his glasses was really doing it for him. He raised his brow bone at the skeleton squirming in his grasp, keeping his cool and letting Sans make the next move. 

“i’m- i’m up for anything. i mean- shit- for whatever punishment you think is gonna- _oh fuck._ ”

Gaster was puzzled for a second at the sudden outburst but then he caught the bright glow coming from his colleague's pants. He knew that Sans’s magic was a brilliant shade of blue, but he had never craved seeing it as much as he did now. Acting purely on instinct he shot his hand out towards the other skeleton’s crotch, making them both groan when he cupped the throbbing cock waiting for him there. 

“Hard at work?” Gaster smirked at his own wordplay knowing just how much Sans would enjoy that little addition. He took his time to really get a feel of what he’d been dreaming of for months and to coax more delicious sounds out of the other skeleton. “I didn’t know the role of my assistant was so stimulating for you.”

Sans was the one to surprise him then, moving the hand that Gaster wasn’t holding down to mirror what Gaster was doing to him. The fact that Gaster was sporting his own tent had slipped his mind until he felt Sans grab him through his pants and squeeze hard. 

“judging me when you’re just as bad hey?” Sans clicked his now formed tongue behind his teeth, drawing Gaster’s attention to the glowing blue appendage in his mouth that was dripping enough to be considered obscene. “gonna have to look into company policy about that, unless you make it worth my while.”

Gaster cursed under his breath as Sans started to practically jerk him off through his pants. When Gaster returned the favour he was treated to a breathless moan and Sans falling forward to slip between his open legs. The change in position pressed their concealed erections together, making them both gasp. Sans gave Gaster a quick once over to check if this was still ok before grinding into him. His movement was soft and hesitant at first, but when his experiment yielded good results he doubled his efforts. The atmosphere was sweltering as Gaster arched into his assistant who was all but fucking him into the chair. 

“Sans-” Gaster gripped hold of Sans’s hips on a particularly hard thrust to try and bring him even closer, the last shreds of his dignity disappearing with each delicious pass. “Gods, keep doing that.”

“you sure ‘dings?” Sans replied with a wink despite his tone being thick with arousal. “i’m- shit- pretty sure fucking on company property is against the rules.”

Gaster snapped. Sans had successfully driven him to a point where he could no longer take the tension between them both when what he wanted was within his reach. He made a sound like a caged beast before standing, taking Sans with him, and slamming him onto his desk. 

“Fuck the rules.” 

Gaster didn’t give Sans any time to process what was happening before he moved down to kiss him. He wanted to wipe that smug look of the other skeleton’s face for good. Sans moaned into the kiss, moving his hands to start to fumble with the buttons on Gaster’s lab coat. With how shoddily dressed Sans was Gaster didn’t have the same issues, only pausing their heavy petting to remove the other skeleton’s pants. Gaster took a moment to admire his handiwork; Sans was sprawled on his open lab coat with his shirt pushed up, completely bare from the ribs down while he was still dressed. 

Gaster trailed one hand down Sans’s ivory spine while pumping his assistant's cock with the other, using the slick gathered on his fingers to then move lower and locate the entrance in his pelvis. 

“woah, easy-” Sans spluttered when he felt Gaster pushing his fingers in hard, but his protests died when those fingers hooked to stimulate a spot inside him that made him jack-hammer on the desk. “fuck, oh gods- please-please more!”

“With pleasure, Sans.”

Gaster chuckled darkly, feeling his own length pulse against his unbuttoned fly as he watched his fingers through Sans’s translucent magic. He upped his pace, intent on making Sans squirm while he used his free hand to push his pants down. He noticed the way his assistant's eyelights became wide when Gaster pulled his fingers out and teased the head of his purple cock around Sans’s entrance instead. 

It was hard to describe how incredible pushing into Sans felt after the months of back and forth between them, but their joint cries of ecstasy was certainly a good start. Gaster watched as Sans’s face contorted in pleasure as his hands balled into fists, knowing that he could spend hours watching him fall apart. But that was going to have to wait for another time, right now what they both needed was a quick and hard fuck to gain the release they were so desperately craving. Gaster waited as long as he could for Sans to adjust before he fell forward and started screwing him into the desk. 

It was clear to Gaster that Sans was in the wrong profession, his wanton moans easily able to rival any whore. The smaller skeleton had wrapped his legs around Gaster’s back, eagerly meeting his thrusts as much as he could in his pinned positions. It got to a point where every thrust of Gaster’s hips would make Sans arch further off the desk, his leaking cock sandwiched between them and staining the front of Gaster’s coat. As their climaxes grew closer Gaster made the mistake of looking right into Sans’s eyes, the intenseness of the glowing lights being enough to make his soul start to flutter.

A few more thrusts and Sans tightened around him, throwing his head back with a silent scream as his release spilled between them. Sans was beautiful, and the fact that Gaster had been the one to get him to feel this good was just what he needed to find his own peak. He burned that image into his memory before screwing his sockets shut and came hard in the velvety walls of Sans’s magic. Wary of making the other skeleton uncomfortable, Gaster pulled out and collapsed back into his chair. Watching his magic drip out of Sans’s spent hole while he got his breath back was a very pleasant bonus. 

“so... if you were to guess, how far is it from here to the control room?” 

Gaster’s eyes widened in surprise. Sans hadn’t even sat up and the question was asked so casually as if he hadn’t just had Gaster’s cock buried inside him. 

“Five minutes, why do you ask?”

“well, unless you’ve got a huge exhibitionist kink-” Sans pushed himself up on the desk to shoot Gaster another wink before gesturing to a spot on the wall behind him. “we kinda have to deal with that.” 

Gaster followed his assistant's line of sight before burying his skull in his hands and groaning loudly at their mistake. 

For two of the underground’s most brilliant minds, you would have thought one of them would have noticed the flashing red light of the camera feed being on record beforehand.

**Author's Note:**

> come bother me on my nsfw tumblr [here!](https://megalotrash.tumblr.com)


End file.
